Foretravel Owners' Forum

Foretravel Motorhome Forums => Foretravel Tech Talk => Topic started by: dwest on April 15, 2014, 09:27:20 am

Title: Fuel mileage dropped after running out of fuel.
Post by: dwest on April 15, 2014, 09:27:20 am
Last month, we had the bad experience of running out of fuel. Fuel gauge is not functioning correctly. During the next tank of fuel I noticed that the mpg was as much as a mile per gallon off. Drove about 800 miles. Fuel filter looks clean. Do you think running out of fuel caused the lower mpg? Also, in the last hundred miles it seems to be back to normal.

David
Title: Re: Fuel mileage dropped after running out of fuel.
Post by: John S on April 15, 2014, 09:45:01 am
Do not see why it would, but I would love to know if there was a reason other then difference in filling.  Maybe you used the little reserve in the bottom and the refill took that into account and the next fill had it already there.
Title: Re: Fuel mileage dropped after running out of fuel.
Post by: Dan Stansel on April 15, 2014, 10:52:21 am
I understand there is a way to adjust the fuel gauges to be correct.  Might call Foretravel to see how to do it or someone here may know. :D DAN
Title: Re: Fuel mileage dropped after running out of fuel.
Post by: rsihnhold on April 15, 2014, 12:38:20 pm
When I bought my MH, I wasn't sure if my fuel gauge was calibrated to allow for a very generous amount of warning before the tank was actually empty or just a faulty gauge which would result in the needle being on E with a full 50 gallons left in the tank (essentially a full day of driving).

However, after pumping and draining the tank for changing out the fuel lines, I realized that there must have been some crud on the sensors since the gauge is now displaying the proper amount of fuel in the tank and the gauge/sensors had been malfunctioning before.
Title: Re: Fuel mileage dropped after running out of fuel.
Post by: Keith and Joyce on April 15, 2014, 12:46:38 pm
The only way besides a flow meter to gauge MPG is to fill tank,  drive coach then note how much fuel is used to refill tank.  Calculation is miles since last fill up divided by gallons.

If you filled up with biodiesel your mpg will be lower than with straight diesel.  Also #2 diesel will give you more mpg than #1 or #1/#2 mix.

Biodiesel comes in various mixes i.e. B5, B20 and so on.  It should be on the pump.  Avoid the higher numbers.

Keith
Title: Re: Fuel mileage dropped after running out of fuel.
Post by: gootie on April 15, 2014, 01:26:43 pm
Fuel filter(s) now dirty? My Little VW TDI always gets a mileage boost after replacing the main fuel filter
Title: Re: Fuel mileage dropped after running out of fuel.
Post by: J. D. Stevens on April 15, 2014, 03:32:26 pm
I was able to tweak the adjustments on the fuel gauge sender a couple of times to get reasonable readings. When it got totally flakey, I had FOT put in a new sender. It is a new style. It seems to be working properly. About $120 for the part.
Title: Re: Fuel mileage dropped after running out of fuel.
Post by: dwest on April 15, 2014, 07:46:35 pm
I think I will look into the new part. Silver leaf is doing the calculating. Usually is dead on. Will change fuel filter after watching this next tank full. I feel the filter is the culprit.

David
Title: Re: Fuel mileage dropped after running out of fuel.
Post by: Dave M (RIP) on April 15, 2014, 08:21:15 pm
Seems incredible running out of fuel with a VMSpc (Silverleaf), I ignore the gauge on dash and only regard the VMSpc for fuel burn. it has always been within 1 gal at a 100 gal refill.  Meaning when it sez have used 138.3 gal, a total refill was 139.2 gal.  So I have faith in it. The gauge is all over the place.
Do what makes you happy
Dave M
Title: Re: Fuel mileage dropped after running out of fuel.
Post by: J. D. Stevens on April 15, 2014, 09:13:03 pm
VMSpc is not an option for the C8.3 engine on our coach. The choices for measuring remaining fuel are fuel gauge, trip odometer, hour meter, or measure at the tank. I will be pleased to have a functional fuel gauge again.
Title: Re: Fuel mileage dropped after running out of fuel.
Post by: John Haygarth on April 15, 2014, 11:24:46 pm
At some point I have decided to remove tank and cut a section out and install a glass (or other) section so the level can be viewed. Do not understand why this is not done when making tanks anyway. At least with this kind of thing it may help to see how clean the fuel is as well.
JohnH
Title: Re: Fuel mileage dropped after running out of fuel.
Post by: Pierce & Gaylie Stewart on April 16, 2014, 03:19:54 am
John,

How about drilling a hole in the top and bottom side of the tank, installing shut off valves and then running a vertical sight glass? I use a stick to check fuel level and with exactly 6 gallons per inch on our U300,  it's easy to figure exactly how much fuel is left. I don't even figure how many gallons I put in or anything, just the ODO reading and gallons in the tank.

Pierce
Title: Re: Fuel mileage dropped after running out of fuel.
Post by: dwest on April 16, 2014, 08:54:20 am
I started using a measuring stick as well. Can't argue with measurement!  The issue with running out previously was Silverleaf had been reset during a trip and then lost track of that. With gauge not working correctly, we were then out in harms way and did not realize we we're off about 50 gallons. Some time went by between a few shorter trips and then it happened! Gives a lot of credence to never getting below half a tank without refilling.

Measuring stick is a piece of aluminum. I don't have calculation to how many gallons per inch, but can easily see 1/2 or 1/3 or whatever in about 5 seconds.

David
Title: Re: Fuel mileage dropped after running out of fuel.
Post by: PatC on April 16, 2014, 09:08:24 am
I don't have VMSpc on my mechanical motor.  Figure my mpg the old fashion way -  miles driven/gallons in mathematical formula.  I keep it all in a written fuel logbook, a hard cover record book.  I reset my mechanical trip meter every time I fuel up.  Try to fuel up between 400 to 600 miles.  Works well and I have a accurate, continuous, record of my miles per gallon.
Title: Re: Fuel mileage dropped after running out of fuel.
Post by: J. D. Stevens on April 16, 2014, 09:32:53 am
I don't have VMSpc on my mechanical motor.  Figure my mpg the old fashion way -  miles driven/gallons in mathematical formula.  I keep it all in a written fuel logbook, a hard cover record book.  I reset my mechanical trip meter every time I fuel up.  Try to fuel up between 400 to 600 miles.  Works well and I have a accurate, continuous, record of my miles per gallon.
Ditto! I do like having a functional fuel gauge as well.
Title: Re: Fuel mileage dropped after running out of fuel.
Post by: wa_desert_rat on April 16, 2014, 11:21:14 am
I don't have VMSpc on my mechanical motor.  Figure my mpg the old fashion way -  miles driven/gallons in mathematical formula.  I keep it all in a written fuel logbook, a hard cover record book.  I reset my mechanical trip meter every time I fuel up.  Try to fuel up between 400 to 600 miles.  Works well and I have a accurate, continuous, record of my miles per gallon.

I take it one step further... I don't use the "trip meter" (I use the really old fashioned method of subtracting the miles last time from the miles this time) and I calibrate the odometer using the "mile markers" on the side of most highways. I try to get ten mile markers in on a relatively flat road. My odometer reads 2% slow as of the last calibration. Then it's gallons of fuel pumped into miles driven times correction factor.

One other note: a few years back the State of California discovered an interesting way to defeat their test on gas pump accuracy. A new "chip" in the pump delivers accurate measure up to ten gallons; after that it delivers slightly less  fuel than it indicates. This worked for quite a while since the Weights and Measures inspectors typically used 1-gallon and 5-gallon containers to test the accuracy of the pump's delivery.

Craig